In order to apply a coating liquid such as ink, paint, or varnish to a web of paper or cardboard in a large production operation it is standard to pass the moving web around a large-diameter backing roller that is juxtaposed with an applicator unit that coats the web with a thick layer of the liquid and, downstream therefrom, a dosing unit that removes excess liquid, leaving on the web a coating or film of the desired thickness. The applicator can be a roller (German 3,623,402 of H. Sommer) or tray (European 0.051,698 of W. Damrau). The dosing system can be a mechanical blade (German 3,623,402 of H. Sommer cited above), a rod (German 3,022,955), a scraper (European 0,109,520 of H. Sommer), or a so-called air knife (U.S. Pat. No. 5,368,893 of H. Sommer). In order to maximize production speed it is known to arrange the applicator and dosing units around backing rollers at which the web is supported over its entire width (U.S. Pat. No. 5,460,119 of H. Maroszek).
In the production of a coated paper or cardboard web the applicator and dosing units must be right for the particular type of paper and the type of coating liquid. In particular at high web speeds of 1000 m/min these units must work perfectly and correspond exactly to the requirements of the current run. As a result it is standard in the prior-art systems to have considerable down time while the applicator and dosing units are reset and/or replaced between runs.